The present invention relates to a fuel supply unit consisting of a pump and an electromotor, in which the pump rotor and motor armature are mounted on a common fixed axis and possess a rotation-locking connection. In existing fuel supply units of this type, the pump rotor is either rigidly connected with the motor armature or they are connected together via a tube section which provides common bearing for the pump rotor and motor armature. However, as the stresses which are exerted on the pump rotor bearing in a radial direction are substantially greater than are those forces which are exerted on the motor armature, the end of the shaft which supports the common pump rotor and motor armature bearing is worn far more rapidly than the bearing on the opposite end of the motor armature. This wear is especially marked during dry operation of the pump which occurs occasionally, for example, when the fuel tank is empty and also when using certain newer types of fuel which have relatively poor lubricating properties. Unilateral wear of the bearings has the following disadvantages:
(1) THE MOTOR ARMATURE NO LONGER OPERATES CONCENTRICALLY WITH RESPECT TO THE FIXED AXIS WHICH HAS A DETRIMENTAL AFFECT ON MAGNETIC FORCES;
(2) THE PUMP ROTOR IS ALSO INCLINED AS A RESULT OF THE INCLINATION OF THE MOTOR ARMATURE WHICH RESULTS IN INCREASED UNILATERAL AXIAL FORCES BETWEEN THE PUMP ROTOR AND LIMITING WALL OF THE PUMP;
(3) THE INCLINATION OF THE MOTOR ARMATURE CAUSES EXCESSIVE STRESS TO BE EXERTED ON THE COUPLING BETWEEN THE PUMP ROTOR AND THE MOTOR ARMATURE, THEREBY CAUSING EXCESSIVE WEAR OF THESE ELEMENTS.
Accordingly, these disadvantages result in excessive current assumption by the electromotor and a reduction in the quantity of fuel supplied as well as reduction in the pressure in the pump thus leading very possibly to failure of the fuel supply system.